CN107576373B - Method for judging and correcting detection precision of feed gas flow of synthetic ammonia system - Google Patents
Method for judging and correcting detection precision of feed gas flow of synthetic ammonia system Download PDFInfo
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- CN107576373B CN107576373B CN201710706335.9A CN201710706335A CN107576373B CN 107576373 B CN107576373 B CN 107576373B CN 201710706335 A CN201710706335 A CN 201710706335A CN 107576373 B CN107576373 B CN 107576373B
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Abstract
The invention discloses a method for judging and correcting the monitoring precision of the raw material gas flow of a synthetic ammonia system. The invention discloses a method for judging the monitoring precision of the flow of feed gas of a synthetic ammonia system. On the basis of the method, the invention also discloses a method for correcting the raw material gas flow of the synthetic ammonia system. The method for judging and correcting the detection precision of the flow of the raw material gas of the synthetic ammonia system is suitable for judging the precision of the flow of each pipeline of a fresh hydrogen feeding system of synthetic ammonia and correcting a flow meter according to the judgment precision.
Description
Technical Field
The invention relates to a flow meter precision judging and correcting method, in particular to a flow meter precision judging and correcting method for each pipeline in a fresh hydrogen raw material gas feeding system in the synthetic ammonia industry.
Background
In the synthetic ammonia industry, the produced ammonia gas is the main raw material of chemical fertilizer, urea and the like, and the control of the feeding ratio is very important to ensure the product quality. Plants often employ methods of controlling feed flow to control feed ratio. The flow meter is often accompanied by different degrees of accuracy, so it is significant to determine and correct the accuracy of the flow meter.
The feed ratio is controlled by the feed flow rate, which is typically achieved by controlling the feed flow rates of hydrogen and nitrogen. The hydrogen source is rich, and the common factory adopts the hydrogen generated upstream and newly synthesized and purified hydrogen as the hydrogen feed. And nitrogen is used as a feed after being purified by air separation. The nitrogen feed rate is often controlled to control the hydrogen-to-nitrogen ratio of the ammonia synthesis system.
As shown in figure 1, is a flow diagram of different sources of fresh hydrogen in an ammonia synthesis system, wherein A raw gas and B raw gas are used as the feed of the fresh hydrogen together, and part of the A raw gas directly enters a decarbonization unit to remove CO2And the other part is mixed with the raw material gas of the B strand and then enters a decarburization system for decarburization operation. This is achieved byWhen the load of the raw material gas A is larger than that of the raw material gas B, the load of the decarburization system A can be shared by feeding the raw material gas A into the decarburization system B. Most of CO and CO can be removed through decarburization treatment2While small amounts of CO and CO remain2Further purification is carried out and then the reaction is carried out in an ammonia synthesis system.
The process and nitrogen addition system shown in FIG. 1 are typically located remotely from the ammonia synthesis reaction system, and therefore control after detecting a malfunction in the hydrogen-to-nitrogen ratio will cause a lag. Therefore, it is necessary to perform advanced control in advance by detecting the data of the fresh hydrogen flow rate, and thus it is inevitable to detect several flow meter flow rates and corresponding concentrations as shown in fig. 1. Concentration indexes are accurate, flow data are relatively inaccurate, process control is carried out through the inaccurate flow data, and the expected effect cannot be achieved.
Disclosure of Invention
Aiming at the technical problems of the existing flow meter, the invention provides a method for judging the accuracy of the flow detection of the raw material gas of a synthetic ammonia system, which is calculated by the following formula:
formula (1) (F)4-F2)·H2％(F1)+F2·H2％(F2)＝F6·H2％(F6)
Wherein F1-A feed gas flow
F2-flow of feed gas of B streams
F4B decarburization inlet flow
F5-A decarburization Outlet flow
F6B decarburization outlet flow
H2％(F1)——F1Corresponding hydrogen content
H2％(F2)——F2Corresponding hydrogen content
H2％(F5)——F5Corresponding hydrogen content
H2％(F6)——F6Corresponding hydrogen content
Further, the raw material gas flow rate is corresponding volume flow rate, and the unit is Nm3Hydrogen content refers to the mole percentage of hydrogen.
Further, the hydrogen content data is detected partly by a laboratory and partly by a field instrument in real time, and the detected data is accurate data.
Furthermore, the volume flow data of the raw material gas is flow meter data, and the precision of part of the data is poor, wherein F5And F6To be recognized as accurate data, F1、F2、F4Is relatively inaccurate data.
Further, the accuracy determination method is calculated by the calculation formula, and when the hydrogen percentage changes by 1%, F is determined1、F2、F4The influence amplitude of (1) is large, the grade is low, namely the precision is high, and the corresponding instrument is a relatively accurate instrument; the small influence amplitude is considered to be higher in grade, namely lower in precision, and the corresponding instrument is the instrument to be corrected.
Furthermore, the invention also provides a method for correcting the flow of the raw material gas of the synthetic ammonia system, which is used for correcting the flow of the flow meter of each pipeline in the fresh hydrogen feeding system in the synthetic ammonia industry. The correction method is to correct the meter with low precision by the meter with high precision according to the flow meter precision judgment method.
Further, the method for correcting the flow rate of the raw material gas of the ammonia synthesis system comprises the following steps:
formula (1) (F)4-F2)·H2％(F1)+F2·H2％(F2)＝F6·H2％(F6)
Wherein F1-A feed gas flow
F2-flow of feed gas of B streams
F4B decarburization inlet flow
F5-A decarburization Outlet flow
F6B decarburization outlet flow
H2％(F1)——F1Corresponding hydrogen content
H2％(F2)——F2Corresponding hydrogen content
H2％(F5)——F5Corresponding hydrogen content
H2％(F6)——F6Corresponding hydrogen content
Further, for F1、F2、F4、F5、F6And determining three table values, namely calculating the other two flow values by a formula, wherein the correction deviation is calculated as follows:
δ＝FCal-Fbiao
wherein FCalAs flow correction value, FbiaoIs the flow meter flow.
The raw material gas flow detection precision judgment of the synthetic ammonia system carries out precision judgment on the flow meters of all pipelines from the fresh hydrogen source of the existing synthetic ammonia system, and corrects the flow meters according to the precision judgment, improves the reliability of data, and is suitable for correcting inaccurate flow meters of all pipelines of fresh raw material gas in the synthetic ammonia industry. The original inaccurate flow meter data can be used, so that the hydrogen-nitrogen ratio of the synthetic ammonia feed can be controlled unreasonably. By the method, the flow data can be effectively fed back to the nitrogen adding system, the feeding ratio of the synthetic ammonia can be accurately controlled, and the effect of improving the quality of the synthetic ammonia product can be achieved.
Drawings
FIG. 1 is a process diagram of a source of fresh hydrogen for an ammonia synthesis system.
Detailed Description
The invention is further described below with reference to fig. 1.
The main idea of the invention is to determine the precision sequence of each flow by precision judgment, and then to select the flow with higher precision and lower precision to correct the flow by the known conditions.
The flow is shown in figure 1, wherein the fresh hydrogen in the process has two sources, namely, A-strand raw material gas and B-strand raw material gas, and as the flow of the A-strand raw material gas is far greater than the flow of the B-strand raw material gas, partial materials of the A-strand raw material are shunted to a system B, so that the load of the system A is reduced. Both line A and line B are decarbonized to remove most of the CO2Then the mixture enters methanol to remove trace CO and CO2. Wherein, the process comprises the following steps:
F1-A feed gas flow
F2-flow of feed gas of B streams
F3-A decarburization Inlet flow
F4B decarburization inlet flow
F5-A decarburization Outlet flow
F6B decarburization outlet flow
F7-flow rate of A to B
H2％(F1)——F1Corresponding hydrogen content
H2％(F2)——F2Corresponding hydrogen content
H2％(F5)——F5Corresponding hydrogen content
H2％(F6)——F6Corresponding hydrogen content
The following two independent equations can be listed according to the hydrogen mass balance and the total mass balance of the A strands of raw material gas:
(F4-F2)·H2％(F1)+F2·H2％(F2)＝F6·H2％(F6)formula (1)
For F1、F2、F4、F5、F6In which F is5、F6Is generally an accurate value, and F1、F2、F4According to the above formula, when the hydrogen content is changed by 1%, the influence range of the hydrogen content on each flow is analyzed, and the rank order of the three is determined.
When the data in the process are as follows: a strand of raw material gas flow F1＝1023Nm3Flow rate F of raw material gas of/h and B2＝250Nm3H, B decarbonization inlet flow F4＝380Nm3H, A decarburization outlet flow F5＝630Nm3H, B decarbonization outlet flow F6＝240Nm3The hydrogen content of the feed gas A is 52 percent, the hydrogen content of the feed gas B is 57.5 percent, the hydrogen content of the decarbonization outlet A is 74 percent, and the hydrogen content of the decarbonization outlet B is 88 percent. When F is reduced by 1% of the hydrogen content at the outlet of the decarburization of B by the above formula2Determine if F1Decrease by 0.5%, F4The reduction is 1.2%, so the rank ordering of the two is judged to be F1＞F4Similarly, F can be obtained1＞F2，F4＞F2And is comprehensively expressed as F1＞F4＞F2，F1Highest grade indicates the least accurate need for correction, and conversely F2The scale lowest ratio representation is relatively more accurate and can be used to correct other meters. Since the independent equations can solve for 2 sets of data, it can be considered that F2Is a more accurate flow. For F1、F2、F4、F5、F6And determining three table values, namely calculating the other two flow values by a formula, wherein the correction deviation is calculated as follows:
δ＝FCal-Fbiao
wherein FCalAs flow correction value, FbiaoIs the flow meter flow.
Thus, passing through F2、F5、F6According to the above two formulas, F can be obtained1CalAnd F4Cal. Then will beF1CalAnd F4CalRespectively comparing with the field meter value to obtain corresponding deviation, thereby realizing correction of the flow meter, F1Cal、F4CalAre respectively F1、F4The flow correction value of.
The invention is closely connected with an industrial field and is developed aiming at the partial flow meter inaccuracy problem existing in the field. Firstly, a flow meter detection inaccuracy judging method is disclosed, and then on the basis, a flow correction method is disclosed, namely, the flow with larger deviation is corrected through calculation, so that the flow data is more reliable to use, and the method has great significance for effectively controlling the hydrogen-nitrogen ratio of the synthetic ammonia system.
Claims (6)
1. A method for judging the detection precision of the raw material gas flow of a synthetic ammonia system is characterized by comprising the following steps: the flow precision judging method adopts the following formula to calculate:
(F4-F2)·H2％(F1)+F2·H2％(F2)＝F6·H2％(F6)formula 1
Wherein F1-A feed gas flow
F2-flow of feed gas of B streams
F4B decarburization inlet flow
F5-A decarburization flow rate
F6B decarburization flow rate
H2％(F1)——F1Corresponding hydrogen content
H2％(F2)——F2Corresponding hydrogen content
H2％(F5)——F5Corresponding hydrogen content
H2％(F6)——F6Corresponding to the hydrogen content;
the calculation formula is calculated by material balance, wherein the formula 1 is calculated by hydrogen material balance in the system, and the formula 2 is calculated by total material balance of the A-strand feed gas;
in the volume flow data, F5And F6To be recognized as accurate data, F1、F2、F4Relatively inaccurate data;
formulas 1 and 2 calculate that when the percentage of hydrogen in the A raw material gas is changed by 1 percent, the F is treated1、F2、F4The influence amplitude of (1) is large, the grade is low, namely the precision is high, and the corresponding instrument is a relatively accurate instrument; the grade is higher, namely the precision is lower, and the corresponding instrument is the instrument to be corrected.
2. The method for judging the detection accuracy of the raw material gas flow of the ammonia synthesis system as claimed in claim 1, wherein: each gas flow rate is a volume flow rate in Nm3The hydrogen content refers to the mole percentage and mol percent of hydrogen.
3. The method for judging the detection accuracy of the raw material gas flow of the ammonia synthesis system as claimed in claim 1, wherein: and part of the hydrogen content data is detected by a laboratory, and the other part of the hydrogen content data is obtained by on-line analysis of an instrument.
4. A method for correcting the flow of raw material gas of a synthetic ammonia system is used for correcting the flow of flow meters of all pipelines in a fresh hydrogen feeding system in the synthetic ammonia industry, and is characterized in that: the accuracy judging method according to claim 1, wherein the low-accuracy meter is corrected by the high-accuracy meter.
5. The method of claim 4, wherein the method comprises the following steps: the correction method is calculated by the following formula:
(F4-F2)·H2％(F1)+F2·H2％(F2)＝F6·H2％(F6)formula (1)
Wherein F1-A feed gas flow
F2-flow of feed gas of B streams
F4B decarburization inlet flow
F5-A decarburization Outlet flow
F6B decarburization outlet flow
H2％(F1)——F1Corresponding hydrogen content
H2％(F2)——F2Corresponding hydrogen content
H2％(F5)——F5Corresponding hydrogen content
H2％(F6)——F6Corresponding to the hydrogen content.
6. The method of claim 5, wherein the method comprises:
for F1、F2、F4、F5、F6And determining three table values, namely calculating the other two flow values by a formula, wherein the correction deviation is calculated as follows:
δ＝FCal-Fbiao
wherein FCalAs flow correction value, FbiaoIs the flow meter flow.
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| JPS5325253B2 (en) * | 1972-02-21 | 1978-07-26 | ||
| US5705734A (en) * | 1996-07-17 | 1998-01-06 | Landis & Staefa, Inc. | Automated branch flow calibration in a HVAC distribution system |
| JP4568970B2 (en) * | 2000-07-21 | 2010-10-27 | パナソニック株式会社 | Gas security device |
| CN1199920C (en) * | 2001-12-18 | 2005-05-04 | 石油大学(北京) | Control method of acetylene content at exit of acetylene hydrogenation reactor |
| US7539560B2 (en) * | 2007-01-05 | 2009-05-26 | Dresser, Inc. | Control valve and positioner diagnostics |
| CN100565400C (en) * | 2007-10-29 | 2009-12-02 | 中国石油集团工程设计有限责任公司东北分公司 | Propylene oxidation unit DCS control system in the acroleic acid device |
| DE102009046758A1 (en) * | 2009-11-17 | 2011-05-19 | Endress + Hauser Process Solutions Ag | Self-monitoring flowmeter assembly and method of operation |
| CN103196523A (en) * | 2013-04-01 | 2013-07-10 | 国家电网公司 | Steam turbine performance test standard flow calibration method based on auxiliary flow measurement |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1694107A (en) * | 2005-06-20 | 2005-11-09 | 浙江大学 | Material data correction method and its system |
| CN201990479U (en) * | 2010-12-30 | 2011-09-28 | 上海国际化建工程咨询公司 | Energy-saving device utilizing pressure swing adsorption technique for great production increasing of low-temperature methanol washing and/or liquid nitrogen washing |
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